What to Back Up To

What are you going to do to back up those files? You need to copy them from your hard disk to some other type of medium. There are more hardware options than I could possibly do justice in this space, but a handful stand out, including one or two you don't have to spend any more money on.

Use the hardware Apple gave you—your SuperDrive

You already own at least one suitable device—your SuperDrive. A SuperDrive makes an excellent backup device, but the cost of media may be prohibitive.